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Abstract:

The present invention provides a thin film spacer for maintaining a gap
between a slit valve door and a sealing surface of a slit valve, such as
a metallic insert. The film spacer can extend the life of a seal by
limiting the line of sight exposure of the seal to corrosive gases within
a wafer processing chamber, for example, and by controlling the
compression percentage of the seal. The spacer may be located on an outer
ambient side of the slit valve away from any corrosive gasses that may
exist in the chamber.

Claims:

1. A slit valve door or slit valve, comprising a sealing face and a thin
film spacer on the sealing face for maintaining a minimum gap between the
sealing face and a corresponding sealing surface.

2. A slit valve door or slit valve as set forth in claim 1, further
comprising a seal element on the sealing face for sealing against a
corresponding sealing surface.

3. A slit valve door or slit valve as set forth in claim 1, wherein the
spacer is located outwardly from the seal element on an ambient side
thereof.

4. A slit valve door or slit valve as set forth in claim 1, wherein the
seal element and spacer are formed as an integral piece.

5. A slit valve door or slit valve as set forth in claim 1, wherein the
seal element is continuous along the sealing face.

6. A slit valve door or slit valve as set forth in any claim 1, wherein
the spacer is continuous along the sealing face.

7. A slit valve door or slit valve as set forth in claim 1, wherein the
spacer is formed of a material selected from the group consisting of
elastomers and polymers.

8. A slit valve door or slit valve as set forth in claim 1, wherein the
spacer is a sprayed-on coating.

9. A slit valve door or slit valve as set forth in claim 1, wherein the
spacer is bonded to the sealing surface.

10. A slit valve door or slit valve as set forth in claim 1, wherein the
sealing surface is a multi-plane sealing surface

11. A slit valve assembly comprising:a slit valve having a valve opening
and a sealing surface surrounding the valve opening; anda slit valve door
movable between open and closed positions to respectively permit and
block flow through the valve opening of the slit valve, the slit valve
door having a sealing face for sealing against the sealing surface of the
valve body; anda thin film spacer on at least one of the sealing face of
the slit valve door and the sealing surface of the slit valve for
maintaining a minimum gap between the sealing face and the sealing
surface when the door is in a closed position.

12. A slit valve assembly as set forth in claim 11, wherein the slit valve
door further comprises a seal element on the sealing face for sealing
against the sealing surface of the valve body.

13. A slit valve assembly as set forth in claim 11, wherein the spacer is
located outwardly from the seal element on an ambient side thereof.

14. A slit valve assembly as set forth in claim 11, wherein the seal
element and spacer are formed as an integral piece.

15. A slit valve assembly as set forth in claim 11, wherein the seal
element is continuous along the sealing face.

16. A slit valve assembly as set forth in claim 11, wherein the spacer is
continuous along the sealing face.

17. A slit valve assembly as set forth in claim 11, wherein the spacer is
formed of a material selected from the group consisting of elastomers and
polymers.

18. A slit valve assembly as set forth in claims 11, wherein the spacer is
a sprayed-on coating.

19. A slit valve assembly as set forth in claim 11, wherein the spacer is
bonded to the sealing surface.

20. A slit valve assembly as set forth in claim 11, wherein the sealing
face is multi-plane sealing face.

21. A slit valve door comprising a multi-plane sealing face, and a seal
element received in a groove in the sealing face for sealing against an
opposed multi-plane sealing face of a slit valve, wherein the sealing
element has a portion thereof that protrudes from the groove beyond the
surface of the sealing face to form a seal bead.

22. A slit valve door as set forth in claim 21, wherein the seal element
includes a second portion thereof that protrudes from the groove beyond
the sealing face of the slit valve door, the second portion being spaced
apart from the seal bead and configured to limit line-of sight exposure
of the seal bead to corrosive gasses when the door is installed in a slit
valve assembly and in a closed position.

23. A slit valve door as set forth in claim 21, wherein the seal element
is generally surrounded on three sides by the valve door.

[0002]The present invention relates generally to seal assemblies for
valves and more particularly to slit valve door seal assemblies having
particular use in forming a seal between chambers in vacuum equipment
employed in the semiconductor industry for chip manufacture.

BACKGROUND OF THE INVENTION

[0003]Vacuum systems for manufacturing integrated circuits on wafers are
generally known. A vacuum processing system may typically have a
centralized vacuum chamber, called a transfer chamber, which may be part
of a mainframe, for transferring wafers from one process chamber or load
lock chamber to the next. A vacuum processing system may also typically
have some kind of subsystem, such as a mini-environment, for providing
the wafers to the load locks and other chambers and for collecting them
back in order to send them on to the next system for processing. This
transfer chamber plus the peripheral chambers and staging areas are
sometimes called a cluster tool.

[0004]Between two vacuum chambers, such as the transfer chamber and one of
the process chambers, is a slit valve. The slit valve includes an
elongated rectangular opening for providing physical access between the
two vacuum chambers. For example, when the slit valve is open, a robot in
the transfer chamber may retrieve a wafer from one vacuum chamber and
insert it into another vacuum chamber using a long, thin blade to hold
the wafer.

[0005]After the wafer has been inserted into a vacuum chamber, the slit
valve may be closed and sealed with a slit valve door by, for example, a
pneumatic actuator. The slit valve door usually forms an airtight seal
for the slit valve so that the pressure differential between the two
chambers will not cause a gas leak through the slit valve. A metal insert
may be placed within the slit valve opening in order to form a better
airtight seat for the slit valve door.

[0006]Slit valve doors have typically been made of metal. The
metal-to-metal contact between a slit valve door and the metal insert may
provide a very good seal, but metal-to-metal contact may create
microscopic particles that scrape off of the metal and get into the
otherwise relatively clean environment of the vacuum chambers. Such
particles may land on the wafers in the chambers, thereby contaminating
them. Such contamination is undesirable in the processing of wafers.

[0007]To reduce the contamination by particles from the slit valve, an
O-ring has typically been placed in a groove in the slit valve door.
Thus, metal-to-metal contact is avoided, so no particles are thereby
generated, and the O-ring can provide a satisfactory seal for the slit
valve in many applications.

[0008]However, since the seal between the O-ring and the slit valve is not
static, but rather is constantly being opened and closed such that there
is rubbing and abrading on the O-ring from the slit valve insert, some
particle generation, typically from the 0-ring, still may occur.

[0009]U.S. Pat. No. 6,089,543 discloses a two piece slit valve door
comprising a seal plate mounted on a mounting member. The seal plate,
which actually contacts the slit valve, has a molded-in-place seal for
making the contact and preventing metal-to-metal contact between the door
and the valve. The seal may have a parabolic profile and may be
adhesively bonded within a groove in the seal plate.

[0010]Another consideration when utilizing a resilient seal is controlling
the size of the gap between the door and chamber to eliminate dynamic
metal-to-metal scrubbing of the door and slit valve and/or
overcompression of the seal. Controlling the size of this gap can also
protect the seal from excessive exposure to the harsh chemicals that may
exist in the chamber. Typically, controlling the gap size has involved
tedious adjustment of the door and/or calibration of the actuator.

[0011]Traditional slit valve doors utilizing a resilient seal, such as a
vulcanized fluorocarbon seal or a perfluorinated o-ring, typically have
relied on the clean dry air (CDA) pressure setting of the slit valve
pneumatic actuator to control the size of the gap between the door and
valve and, thus, the seal compression. Fatiguing of the o-ring or
vulcanized seal through dynamic cycling of the slit valve door can result
in plastic deformation of the elastomer which leads to inconsistent
gapping between the slit valve door and the slit valve (and/or insert).
Inconsistent gapping can result in seal over-compression, metal-to-metal
contact between the slit valve door and the slit valve, high exposure
levels of the sealing element to corrosive process gases, and premature
degradation of the seal.

SUMMARY OF THE INVENTION

[0012]The present invention provides a thin film spacer for maintaining a
gap between a slit valve door and a sealing surface of a slit valve, such
as a metallic insert. The film spacer can extend the life of a seal by
limiting the line of sight exposure of the seal to corrosive gases within
a wafer processing chamber, for example, and by controlling the
compression percentage of the seal. The spacer may be located on an outer
ambient side of the slit valve away from any corrosive gasses that may
exist in the chamber.

[0013]Accordingly, a slit valve door or slit valve comprises a sealing
face and a thin film spacer on the sealing face for maintaining a minimum
gap between the sealing face and a corresponding sealing surface. A seal
element on the sealing face can be provided for sealing against the
corresponding sealing surface. The spacer can be located outwardly from
the seal element on an ambient side thereof such that the spacer will not
be exposed to corrosive gasses in the chamber and, therefore, is not
generally subject to accelerated degradation by the same. By maintaining
a minimum gap between the door and the slit valve, the spacer provides
for consistent compression of the seal and, therefore, also can prevent
overcompression of the seal and potential premature wear. The reduced
minimum gap between the door and chamber achieved with the spacer results
in decreased line of sight exposure of the seal to corrosive gasses in
the chamber and, thus, seal life can be extended.

[0014]More particularly, the seal element and spacer can be formed as an
integral piece, and the seal element and/or spacer can be continuous
along the sealing face. The spacer can be formed of a material selected
from the group consisting of elastomers and polymers, and can be a
sprayed-on coating or can be bonded to the sealing surface. The sealing
surface can be planar or multi-planer.

[0015]In accordance with another aspect, a slit valve assembly comprises a
slit valve having a valve opening and a sealing surface surrounding the
valve opening, and a slit valve door movable between open and closed
positions to respectively permit and block flow through the valve opening
of the slit valve. The slit valve door has a sealing face for sealing
against the sealing surface of the slit valve. A thin film spacer is
provided on at least one of the sealing face of the slit valve door and
the sealing surface of the slit valve for maintaining a minimum gap
between the sealing face and the sealing surface when the door is in a
closed position.

[0016]The slit valve door can further include a seal element on the
sealing face for sealing against the sealing surface of the slit valve.
The spacer can be located outwardly from the seal element on an ambient
side thereof, and the seal element and spacer can be formed as an
integral piece. The seal element and/or spacer can be continuous along
the sealing face. The spacer can be formed of a material selected from
the group consisting of elastomers and polymers, can be a sprayed-on
coating, or can be bonded to the sealing surface. The sealing surface can
be planar or can be multi-planar.

[0017]In accordance with another aspect, a slit valve door comprises a
multi-plane sealing face, and a seal element received in a groove in the
sealing face for sealing against an opposed multi-plane sealing face of a
slit valve. The sealing element has a portion thereof that protrudes from
the groove beyond the surface of the sealing face to form a seal bead.
The seal element can also include a second portion thereof that protrudes
from the groove beyond the sealing face of the slit valve door, the
second portion being spaced apart from the seal bead and configured to
limit line-of sight exposure of the seal bead to corrosive gasses when
the door is installed in a slit valve assembly and in a closed position.
The seal element can be generally surrounded on three sides by the valve
door. A thin film spacer can be provided for maintaining a minimum gap
between the slit valve door and a corresponding sealing surface of a slit
valve.

[0018]The foregoing and other features of the invention are more
particularly described in the following detailed description when
considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]In the annexed drawings:

[0020]FIG. 1 is a top schematic view of a prior art vacuum system
including a transfer chamber and a lid;

[0021]FIG. 2 is a perspective view of a transfer chamber with the lid off;

[0022]FIG. 3 is a plan view of the face of a seal plate;

[0023]FIG. 4 is a perspective view of a slit valve door;

[0024]FIG. 5 is a perspective view, partly shown in cross-section, of the
slit valve door of FIG. 4;

[0025]FIG. 6 is an enlarged cross-sectional view of a portion of a slit
valve assembly including an exemplary slit valve door having a spacer in
accordance with the invention shown in closed relationship to a mating
sealing surface of the slit valve;

[0026]FIG. 7 is cross-sectional view of another exemplary slit valve
assembly including a slit valve door having a spacer in accordance with
the invention;

[0027]FIG. 8 is an enlarged portion of FIG. 7;

[0028]FIG. 9 is a perspective view of another exemplary slit valve door in
accordance with the invention;

[0029]FIG. 10 is a front elevation view of the slit valve door of FIG. 9;

[0030]FIG. 11 is a cross-sectional view, taken along line A-A in FIG. 10,
of the slit valve of FIGS. 9 and 10 in another exemplary slit valve.

[0031]FIG. 12 is an enlarged portion of FIG. 11.

DETAILED DESCRIPTION

[0032]Referring now in detail to the drawings and initially to FIG. 1, an
exemplary prior art vacuum processing system is generally indicated at
10. The system 10 comprises a series of vacuum chambers 14 attached to a
central vacuum transfer chamber 12. A pair of vacuum load lock chambers
16 provide a passageway to a mini-environment 18. Pod loaders 20 are
shown attached to the mini-environment 18. This system is an example of a
cluster tool.

[0033]The vacuum chambers 14 may be connected to the transfer chamber 12
at an airtight seal which permits wafers to pass between the chambers 12,
14 and 16 without losing the vacuum in the chambers. The pod loaders 20
are attached to the mini-environment 18 and may be loaded with wafer
cassettes (wafer holders) by a person or by an automated machine that is
part of the over-all automated manufacturing system of the manufacturing
plant or building that houses the vacuum processing system 10. A robot
(not shown) within the mini-environment 18 may move the wafers or
cassettes from the pod loaders 20 to the load lock chambers 16 and back
again. A robot (not shown) with an arm and a blade for moving wafers
within transfer chamber 12 may move the wafers from one of the load lock
chambers 16 to the process chambers 14 and back to one of the load lock
chambers 16.

[0034]The vacuum chambers 14 may be any of several types of process
chambers, such as a chemical vapor deposition (CVD) chamber, a physical
vapor deposition (PVD) chamber, an etch chamber, etc., for performing on
a wafer some type of process in a series of many processes for
manufacturing integrated circuits on wafers.

[0035]In FIG. 2 the transfer chamber 12 is shown with its lid removed so
that the interior of the transfer chamber 12 is visible. Several slit
valves with openings 24 can be seen, as can slit valve inserts 28, 30, 32
and 34. Circular opening 36 supports a robot with an arm for moving
wafers inside the transfer chamber 12, but the robot is not shown in this
drawing so other details of the transfer chamber 12 may be visible.
Openings 38 provide access for an actuating cylinder for manipulating a
slit valve door, the face of which is shown in FIG. 3. The actuating
cylinder and the slit valve door are not shown so that other features in
the transfer chamber 12 may be visible. An example of a slit valve door
and actuating cylinder is shown and described in U.S. Pat. No. 5,226,632,
which is incorporated herein by reference.

[0036]FIG. 3 shows the front face plate of the slit valve door 40. On
front face 48 of seal plate 42 is a molded-in-place seal 50 for
contacting with a slit valve insert 28, 30, 32, 34, or a seat portion
formed thereon. The molded-in-place seal 50 is molded into a groove 58
formed around the periphery of front face 48. The seal may be vulcanized
to the seal plate 42. Thus, in the manufacturing of seal plate 42, the
seal 50 may be permanently attached to the seal plate 42. The seal 50 may
be adhesively bonded to the metal surface of groove 58.

[0037]This type of slit valve door 40 may be actuated in a direction
perpendicular to the plane in which its front face 48 is held by an
actuating cylinder that protrudes out of opening 38. The seal 50 may
match angular face 54 of the inner portion of insert 28. The actuating
cylinder protruding out of opening 38 pushes slit valve door 40 up
against slit valve insert 28 such that the molded-in-place seal 50
engages surface 54 making an airtight seal all around opening 56. Thus,
when slit valve opening 24 is closed by slit valve door 40, the pressure
in either the transfer chamber 12 or the process chamber 14 may change as
needed without leakage between the two chambers.

[0038]Referring now to FIGS. 4 and 5, a slit valve door is designated
generally by reference numeral 64. The slit valve door 64 includes an
annular seal 72 that preferably is molded into an annular groove 74 in
the front face of the door. The molded-in-place seal 72 may have a bottom
contour that matches the contour of the groove 74. As shown, the groove
74 may have upwardly curving edges or sides that end almost vertical, or
perpendicular, to front face 70. The groove surface may have a suitable
roughness to enhance the adhesion between the seal material and the
groove.

[0039]The seal 72 may be made of any suitable material that preferably
does not generate many, if any, particles under the dynamic loading
experienced by the seal, such as a variety of fluorocarbon and perfluoro
elastomers that suit the requirements of wafer processing. Suitable seal
materials are well known in the art. The seal 72 may additionally or
alternatively be bonded to the door 64 by use of a suitable bonding
agent.

[0040]Turning to FIG. 6, which is a sectional view taken along the plane
62 in FIG. 4, a slit valve assembly 60 is illustrated including an
exemplary slit valve door 64 having a thin film spacer or bumper 98 in
accordance with the invention. The thin film spacer 98 is located between
the sealing surface 70 of the slit valve door 64 and a sealing surface 80
of a slit valve 81 for maintaining a gap 82 therebetween. The thin film
spacer 98 prevents the sealing surfaces 70 and 80 from contacting each
other, and operates to maintain the minimum distance therebetween without
the need to precisely calibrate the actuator and/or adjust the slit valve
door 64 for such purpose. Thus, the actuator generally can be configured
to apply a force adequate to compress the seal 72 a desired amount
without the need to account for potentially overcompressing the seal 72.

[0041]The spacer 98 also allows a much smaller gap 82 to be achieved than
would otherwise generally be possible. As will be appreciated, a smaller
gap limits the line-of-sight exposure of the seal 72 to the corrosive
gaseous flow within the chamber, which can extend the life of the seal
72.

[0042]The thin film spacer 98 can be positioned on either side or both
sides of the seal 72. In the illustrated embodiment, the spacer 98 is on
the outer ambient non-process side of the sealing 72, opposite the inner
chamber process side. This position minimizes spacer material degradation
due to exposure to the corrosive gasses of the chamber. The spacer 98 may
or may not be attached to the slit valve door 64, but in general it will
be firmly secured thereto to reduce mechanically-abraded particle
generation under the spacer 98. Alternatively, the spacer 98 can be
adhesively adhered, coated or sprayed, or chemically joined to the slit
valve door 64.

[0043]It will be appreciated that the seal 72 may have the cross-sectional
shape shown in FIG. 6. The seal 72, however, would normally be compressed
between the opposed/mating sealing surface 80 of the slit valve 81 and
the front face 70 of the door 64. Thus, the configuration would be
different than that schematically depicted in FIG. 6. For instance, the
seal may undergo compression as described in U.S. Pat. No. 6,089,543,
which is hereby incorporated herein by reference.

[0044]The dimensions (e.g., width and thickness) of the spacer 98 can be
designed to accept maximum application loads from differential pressure
forces and worst-case CDA pressure settings. At such maximum application
loads, the spacer 98 can be designed to yield virtually no deflection,
allowing for consistent seal compression and gap control between the door
64 and the slit valve 81 regardless of the spacer material's fatigue
strength and thermal stability throughout numerous dynamic cycles and
high temperature softening.

[0045]In the compressed seal state, current slit valve door sealing
elements typically yield a gap 82 of about 0.015'' or greater. The thin
film spacer 98 can be used to minimize the gap to several magnitudes
smaller than 0.015''. Such gap sizes are generally not possible with
other types of spacers, such as spacer blocks, for example. The smaller
gap 82 limits the volume of corrosive gases that may attack the seal 72
during the wafer processing cycle, which as mentioned can result in
increased seal 72 life. Further, because the spacer 98 generally reduces
or eliminates the extent to which the seal can be compressed, seal
degradation do to overcompression can also be reduced or eliminated.

[0046]Turning to FIGS. 7 and 8, another exemplary slit valve assembly 60
is illustrated including a slit valve door 64 in accordance with the
invention. The slit valve assembly 60 is similar to the slit valve
assembly shown and described in connection with FIG. 6. As such, the slit
valve door 64 may be actuated in a direction perpendicular to the plane
in which its front face 48 is held by an actuating cylinder, and the door
64 seals against an angled sealing face of the slit valve 81 (or insert).
Spacer 98 maintains gap 82 between the slit valve door 64 and the slit
valve 81 in the manner previously described.

[0047]Turning now to FIGS. 9-12, another exemplary slit valve assembly 60
is illustrated. The slit valve assembly 60 includes a slit valve door 64
having a multi-plane sealing face 102 for sealing against a corresponding
sealing face 80 of the slit valve 81. The multi-plane sealing face 102
includes a seal 72 molded into an annular groove 74.

[0048]The seal 72 is similar to the seals shown and described above. In
this embodiment, however, additional elastomeric material 106 adjacent
the seal 72, best seen in FIG. 12, is provided for blocking exposure of
the seal 72 to the corrosive chemicals in the chamber when the valve is
closed. The seal 72 and barrier material 106 can be formed as a unitary
piece as illustrated. The barrier elastomeric material 106 generally
extends above sealing surface 80 of the door 64 and is provided on both
the ambient and chamber sides of the seal 72, but may also be provided
only on one side of the seal 72, such as the chamber side, for example.

[0049]The elastomeric material 106 on the chamber side typically can be
subject to degradation due to exposure to the corrosive gasses of the
chamber. As will be appreciated, however, since the elastomeric material
106 is generally non-functional with respect to performing a sealing
function, any such degradation typically will not impact the ability of
the slit valve door 64 to seal properly. Thus, by blocking exposure of
the seal 72 to chemicals in the chamber, the barrier elastomeric material
106 can extend the life of the seal 72.

[0050]In addition, a spacer, such as spacer 98 shown and described above,
can be provided on the multi-plane sealing face 102 adjacent the seal 72.
Although not shown in this embodiment, the spacer would operate in a
similar manner to maintain a minimum gap 82 between the sealing surfaces
70 and 80.

[0051]It will be appreciated that although the spacer 98 has been shown
and described as attached to the slit valve door 64, it could also be
provided on the slit valve sealing surface (e.g., insert) without
departing from the scope of the invention. Further, aspects of the
invention are can be applied to any type of slit valve as well as other
valve types wherein maintaining a minimum gap between mating sealing
surfaces is desired.

[0052]Further, the use of the term "ambient side" in the above description
generally refers to the side of the seal opposite any corrosive gasses
(e.g., the "process side"). Accordingly, the ambient side may be open to
the atmosphere, or may be exposed to another chamber that contains gasses
that are at least somewhat less corrosive than the gasses on the opposite
side of the seal. In some applications there may not be an ambient side
of the seal. This can be the case, for example, if both sides of the seal
have corrosive gasses.

[0053]Although the invention has been shown and described with respect to
a certain preferred embodiment or embodiments, it is obvious that
equivalent alterations and modifications will occur to others skilled in
the art upon the reading and understanding of this specification and the
annexed drawings. In particular regard to the various functions performed
by the above described elements (components, assemblies, devices,
compositions, etc.), the terms (including a reference to a "means") used
to describe such elements are intended to correspond, unless otherwise
indicated, to any element which performs the specified function of the
described element (i.e., that is functionally equivalent), even though
not structurally equivalent to the disclosed structure which performs the
function in the herein illustrated exemplary embodiment or embodiments of
the invention. In addition, while a particular feature of the invention
may have been described above with respect to only one or more of several
illustrated embodiments, such feature may be combined with one or more
other features of the other embodiments, as may be desired and
advantageous for any given or particular application.